Acute kidney injury (AKI) is common in critically ill patients. Serum creatinine is a poor marker of renal function. The lack of progress in the prevention and treatment of AKI may be attributable to poor physiologic markers for early and reliable diagnosis of AKI in reseach studies. Urinary IL-18, neutrophil gelatinase- associated lipocalin (NGAL), and cystatin C are three promising biomarkers for the early detection and potential risk-stratification of AKI. The first aim of this pilot study is to evaluate urine IL-18, NGAL, and cystatin C as biomarkers for the the early detection of AKI in patients with sepsis and/or acute lung injury. The second aim is to determine if urinary IL-18, NGAL, and cystatin C concentrations can risk-statify patients with AKI in terms of the need for renal replacement therapy and in-hospital mortality. The results from this study will help later guide a definitive large multicenter study by developing the study processes and data collection; guiding duration of sample collection and overall sample size for event rates; identifying important subgroups of AKI amenable to study with biomarkers, and finally by developing a biomarker panel for the early and reliable diagnosis of AKI in the ICU setting that has incremental prognostic value. Relevance to public health: In 2006, our ability to diagnose abupt kidney failure is inaccurate and inefficient. Earlier recognition of abrupt kidney failure via newly discovered proteins in the urine will aid health care providers in making a prompt diagnosis, and may predict how severe the kidney failure will be. Furthermore, it will help researchers to perform efficient studies of drug development studies to improve kidney failure by enabling them to identify and enroll patients will kidney failure more rapidily. [unreadable] [unreadable] [unreadable]